The present invention relates to basic zirconium complexes and methods of making and using the same in antiperspirants. More particularly, the invention is directed to the production and use of basic zirconium carbonates and basic zirconium-amino acid compounds in highly acidic aluminum and/or zirconium antiperspirant systems.
It has been known in the art for some time that zirconium salts provide exceptionally effective antiperspirant properties. Such zirconium compounds have included particularly the acidic zirconium salts, such as zirconium oxy chloride or zirconyl chloride, zirconium hydroxy chloride, and other halide and sulfate substitutes of the salts. However, the zirconium salts are extremely acidic and irritating to the skin. For example, a solution of zirconyl chloride which is effective as an antiperspirant has a pH of only about 0.8 and a solution of zirconyl hydroxy chloride which is effective as an antiperspirant has a pH of only about 1.2. As a result, it is necessary to buffer these solutions up to a pH which is suitable for application to the human skin, i.e., up to at least about 3 to 5.
A number of prior attempts have been made in the art to buffer solutions of zirconium salts or to form zirconium complexes which take advantage of the effectiveness of zirconium compounds. One early attempt included the development of sodium zirconium lactate for use in cologne-stick type formulations. This lactate complex salt was sufficiently alkaline (pH 8.5), but was ineffective as an antiperspirant, and was repeatedly implicated in the generation of "zirconium granulomas" in some users.
Other attempts to make use of the acidic zirconium salts involved the buffering of solutions of these salts with urea (see U.S. Pat. No. 2,814,584 to Daley) or water soluble amino acids (see U.S. Pat. Nos. 2,814,585 to Daley and 2,854,382 to Grad) or aluminum hydroxy halides (see U.S. Pat. No. 2,906,668 to Beekman).
More recently, various derivatives have been formed incorporating zirconium compounds, including the amine-amide derivatives of U.S. Pat. No. 3,407,254 to Siegal et al., and the polyhydroxy derivatives of U.S. Pat. No. 3,405,153 to Jones and Rubino.
In addition, Rubino copending application Ser. No. 418,712, now U.S. Pat. No. 4,017,599, entitled "Aluminum-Zirconium Anti-Perspirant Systems With Salts Of Amino Acids", and other related copending applications describe other systems in which amino acids have been incorporated in aluminum-zirconium complexes to offset the acidity of the zirconium and aluminum as well as provide other advantages to the antiperspirant. Nevertheless, still more efficient and advantageous methods are being sought to combat the acidity of aluminum and/or zirconium while at the same time maintaining or improving antiperspirant efficacy.